As medical containers such as bags for infusions, medial solutions, enteral nutrients, or the like, soft bags are used which are obtained from polyethylene, polypropylene, polyvinyl chloride, or the like and made into a bag by blow molding or heat sealing, in addition to glass bottles of the related art. Since such soft bags are light-weighted, have small volumes when the bags are disposed, and even do not require ventilation needles that cause nosocomial infection occurring during administration, soft bags are mainstream.
A film used in the soft bags of the related art is composed of a polyolefin material including polyethylene, polypropylene, or the like in order to reduce amount of eluted materials in steam autoclaving, and to maintain transparency and flexibility. However, oxygen transmission rate of the polyolefin material is large. That is, in order to prevent quality degeneration of a medical solution caused by an oxygen gas from outside, Patent Document 1, or the like has proposed that a soft bag should be packed with an outer packaging material having a high oxygen barrier property. Examples of such an outer packaging material are those including a layer formed of a metal foil, an inorganic vapor-deposited film, and the like.
However, amino acid infusions, fat infusions, and the like are mixed up with the air during dissolution, mixing, suspension, agitation, transfer by pump in a preparation and filming processes, causing the air to remain in such medical solutions as dissolved oxygen. The concentration of the dissolved oxygen is 3 to 50 ppm, and it is known that the dissolved oxygen brings about oxidation degradation of the medical solution. A reaction rate of the oxidation degradation is logarithmically promoted together with temperature. In other words, the oxidation degradation is dramatically accelerated in steam autoclaving. In order to prevent this, a method of putting or laminating a deoxygenating agent inside an outer packaging of an infusion bag, filling an inert gas into the outer packaging of an infusion bag, filling an infusion bag with a medical solution while being substituted with an inert gas, or adding antioxidants to a medical solution, has been invented in Patent Documents 2 and 3, and the like, and implemented. Putting and laminating a deoxygenating agent and filling with an inert gas are effective in suppressing oxidation degradation, but there are concerns that incorrect administration will cause damage or pinholes on the outer packaging that has a barrier property. Furthermore, since a dry lamination method that uses an organic solvent as a medium is used in laminating of the previously-applied art, not only is an eluted material an amount that is not negligible even though the amount is within the standard of the elution test prescribed in Japanese Pharmacopoeia, but also incorporation of foreign substances into the interface of lamination that is exposed during a lamination process is concerned. In addition, as antioxidants to be added to a medical solution, a vitamin C (ascorbic acid), a vitamin E (tocopherol), a BHT (dibutylhydroxytoluene), a BHA (butylhydroxyanisol), a sodium erythorbate, a sodium sulfite, a sulfur dioxide, a coffee bean extract (chlorogenic acid), a green tee extract (catechin), a rosemary extract, and the like are exemplary examples, but among these, a sulfite ion material is widely used as an additive due to the fact that it is highly effective in antioxidation. However, the material is not favorable for a human body since it can be the cause of anaphylactic shock, or the like.
Due to the above background, the following invention has been proposed, which gives an oxygen barrier property or an oxygen absorbing function to a container itself that directly contacts to a medicinal solution.
Patent Document 4 has proposed a five-layered structure that is obtained by making “a polyamide, a polyester, or a polyolefin layer”, “a tie layer”, “a core layer of an ethylene vinyl alcohol copolymer”, “a tie layer”, and “a polyolefin solution-contacting layer” in an order from outside into a film with a cast co-extrusion method. The structure of the publication is excellent in the oxygen barrier property, but has no self-oxygen absorbing ability. In addition, since film preparation in a roll shape by the way of casting makes a solution-contacting face exposed to outside in a soft bag preparation process, it was necessary to set up a countermeasure regarding the incorporation of foreign substances into the bag.
Patent Document 5 has proposed a multi-layered structure obtained by making into a film at least “an oxygen barrier layer composed of an ethylene vinyl alcohol copolymer”, “an oxygen-absorbing gas barrier layer a”, “an oxygen-absorbing gas barrier layer b”, and “a heat-sealed resin layer” in order from the outside with a co-extrusion method. The structure in publication has excellent oxygen barrier property and the oxygen absorbing property under an ambient temperature environment. But, the ethylene vinyl alcohol copolymer of the outermost layer is poor in a damp-proofing property and is not favorable as it turns white in a medical container that has undergone a hydrothermal treatment such as steam autoclaving.